This self-portrait of NASA's Mars rover Curiosity combines 66 exposures taken by the rover's Mars Hand Lens Imager (MAHLI) during the 177th Martian day, or sol, of Curiosity's work on Mars (Feb. 3, 2013). Image credit: NASA/JPL-Caltech/MSSS› Full image and caption

Mission Status Report

PASADENA, Calif. - NASA's Mars rover Curiosity is expected to resume science investigations in a few days, as engineers quickly diagnosed a software issue that prompted the rover to put itself into a precautionary standby status over the weekend.

Curiosity initiated this automated fault-protection action, entering "safe mode" at about 8 p.m. PDT (11 p.m. EDT) on March 16, while operating on the B-side computer, one of its two main computers that are redundant to each other. It did not switch to the A-side computer, which was restored last week and is available as a back-up if needed. The rover is stable, healthy and in communication with engineers.

The safe-mode entry was triggered when a command file failed a size-check by the rover's protective software. Engineers diagnosed a software bug that appended an unrelated file to the file being checked, causing the size mismatch.

"This is a very straightforward matter to deal with," said the project manager for Curiosity, Richard Cook of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We can just delete that file, which we don't need any more, and we know how to keep this from occurring in the future."

The mission's science observations have been on hold since a memory glitch on the A-side computer on Feb. 27, which prompted controllers to command a swap from the A-side computer to the B-side computer. That operator-commanded swap put Curiosity into safe mode for two days. The rover team restored the availability of the A-side as a backup and prepared the B-side to resume full operations.

Cautiously bringing Curiosity out of safe mode status on the B-side is expected to take a couple of days. A four-week moratorium on sending commands to the rover will begin April 4 due to solar system geometry of Mars passing nearly directly behind the sun from Earth's perspective. The moratorium is a precaution against interference by the sun corrupting a command sent to the rover.

NASA's Mars Science Laboratory project is using Curiosity and the rover's 10 science instruments to investigate environmental history within Gale Crater, a location where the project has found that conditions were long ago favorable for microbial life. JPL, a division of the California Institute of Technology in Pasadena, manages the project for NASA's Science Mission Directorate in Washington.